Voltage drop cause THD to rise? & Possibly clipping?

[qu1cks1lver56]

Well I successfully fried the coils in my 2515's in 2 days There was no clipping on the outputs of the amps, except slightly on a 0db sine wave, which music comes no where close to in level. There was NO clipping with a -5db sine wave.

My question is, since I had some hardcore voltage drop if I let it play for more than 30seconds-a minute, will voltage drop (14.4ish to 12.0, or possible less I tried not to let it get that low) cause the THD on an amp to rise significantly and clip the output? More specifically, on a RF T1k (elite)

[Boon]

Did you scope it with a load connected or not?

If you scoped it without a load it's not a lot of good since the rail voltage will drop tremendously when it flows current.

But yeah, as input voltage drops the rail voltage drops proportionately. Car amp power supplies use an unregulated toroidal transformer most of the time so effectively you just have a ratio. Say you have a 5:1 transformer, with 14.4v in you get 72v rail-rail which gives you ~650wrms @ 1 ohm clean. Drop the input to 12v and you only get 450wrms @ 1 ohm before you hit clipping. So yeah, THD goes through the roof because there simply isn't enough voltage available so the wave squares off.

To kill a 2515 is a solid effort. I ran mine on a fairly clipped ~1500wrms each and they only ever got a bit warm. Either you have DC offset on the outputs or you were clipping the tits off it.

EDIT: That amp is probably ~6.2:1 so at 12v you only get 700wrms (26vacrms) before it clips

Edited August 26, 2010 by Boon

[qu1cks1lver56]

I scoped it with a load.

And see, I hear stories like that all the time, the only thing I can think of, that might've helped them get as hot as they got, is that the motors were in the sealed chambers of my 4th order. And well DD doesn't recommend running their woofers in a sealed enclosure. And if the amps did start clipping when the voltage dropped, and the coils started getting hot, and then having no port to move some air through to pull fresh air in, all they did was move around in hot air. Plus I couldn't smell them when the motors were sealed up so no telling how long I played them while they were hot before the first one let go.

I'm debating on getting recones, and running them inveted in the box, and seeing how they hold up then, and I'll make sure to be super easy on them for a week or 2, I wasn't hammering on them (not even close) and being very conscious of DD's recommended break in time. But I couldn't help myself, I let it eat a few times.

Right now I'm looking on some input on what others think I should do, the inverted thing seems like it would work if I keep the volume down until I get an alt to keep up with the current draw.

[STEvil]

what did you use for a load?